Air Quality Criteria for Lead Volume II of II - (NEPIS)(EPA) - US ...

AX4-26
Reference, Study
Location, and
Period Study Description
Mexico (cont’d)
Hernandez-Avila
et al. (2002)
Mexico City
1994
Téllez-Rojo et al.
(2002)
Mexico City
1994-95
Table AX4-7 (cont’d). Bone Lead Studies in Pregnant and Lactating Subjects
Aim to evaluate the effects of
maternal bone Pb stores on
anthropometry at birth in 223
mother-infant pairs.
Anthropometric data were
collected within the first 12 hr
following delivery. Maternal
information was obtained 1 mo
after delivery (mean age 24.4 ± 5.4
yr). Transformed anthropometric
measurements to an ordinal 5category
scale, and association of
measurements with other factors
evaluated with ordinal logisticregression
models. Cumulative
Odds Model.
Evaluated the hypothesis that
lactation stimulates Pb release
from bone to blood.
Cross-sectional examination of
breastfeeding patterns and bone Pb
as determinants of PbB among 425
lactating women (mean age 24.8
±5.3 yr) for 7 mo after delivery.
Bone Pb at 1 mo postpartum.
Maternal blood samples and
questionnaire information
collected at delivery and at 1, 4,
and 7 mo postpartum. Generalized
estimating equations.
Lead Measurement (SD or range)
PbB in µg/dL, Bone Pb in µg/g Bone Mineral Findings, Interpretation
Cord blood 7.01 (±3.5), maternal PbB 8.82 (± 4.0), tibia 10.70 (±7.58,
adjusted for negative values), patella 15.39 (±11.18, adjusted for negative
values). Maternal PbB increased linearly by 0.096/µg of tibia Pb and
0.078/µg patella Pb. Umbilical cord PbB increased by 0.111/µg tibia Pb
and 0.061/µg patella Pb. Birth length of newborns decreased as tibia Pb
levels increased (odds ratio of 1.03/µg/g bone mineral [95% CI: 1.01,
1.06]).
Mean PbB decreased with time postpartum: 1 mo 9.4 (±4.4), 4 mo 8.9
(±4.0), 7 mo 7.9 (±3.3).
Tibia 10.6 (11.6 after correction for negative values), patella 15.3 (16.9 after
correction). After adjustment for bone Pb and environmental exposure,
women who exclusively breastfed their infants had PbB levels that were
increased by 1.4 µg/dL and women who practiced mixed feeding had levels
increased by 1.0 µg/dL, in relation to those who had stopped lactation.
A 10 µg Pb/g increment in patella and tibia bone Pb increased PbB by 6.1%
(95% CI: 4.2, 8.1) and 8.1% (95% CI: 5.2, 11.1), respectively.
Compared with women in the
lower quintiles of the distribution
of tibia Pb, those in the upper
quintile had a 79% increase in
risk of having a lower birth
length newborn (OR ratio 1.79;
95% CI: 1.10, 3.22). Patella Pb
was positively related to the risk
of a low head circumference
score; this score remained
unaffected by inclusion of birth
weight. The increased risk was
1.02/ Fg Pb/g bone mineral (95%
CI: 1.01, 1.04). Odds ratios did
not vary substantially after the
authors adjusted for birth weight
and other important determinants
of head circumference.
They concluded that their results
support the hypothesis that
lactation is directly related to the
amount of Pb released from
bone.